These five tips should help keep the meringue on your pies from weeping:
• Make meringue pies on dry, low-humidity days.
• Be careful not to overbake your meringue—doing so causes the egg whites to shrink and squeeze out small tears of moisture. Always check your pie at the minimum baking time.
• Undissolved sugar in the egg whites may cause weeping. To make sure the sugar is adequately dissolved, mix the egg whites and sugar at low speed until the mixture feels perfectly smooth with no graininess when you rub a little bit between your thumb and fingers. You might also try using superfine sugar—it dissolves much more quickly than regular white sugar.
• Be sure to prepare meringue before preparing the pie filling so it is ready to spread while the filling is still hot. The filling’s residual heat will “cook” the meringue onto the filling and make it much less likely to leak or shrink.
• Make sure to seal the meringue completely to the edge so it touches the crust.